Under normal circumstances, there are many muscles around the mouth, such as labial, lingual and buccal muscles, etc. The mutual balance of these muscles maintains the normal shape of the dental arch. The bad habit of biting the lower lip breaks the balance of muscles inside and outside the mouth, the upper front teeth always bite on the outer side of the lower lip, the upper front teeth will produce a force toward the lingual side of the lower lip and the mandibular anterior region, which leads to the lingual tilt of the lower front teeth, crowding, jaw recession, and at the same time increases the pressure on the palatal side of the upper front teeth, which makes the upper front teeth tilt and shift toward the labial side, a gap appears, and the anterior part of the maxilla protrudes. A deep overlay is formed between the upper and lower anterior teeth, and deep overlay, and the lower teeth are not visible when the upper and lower jaw anterior teeth bite together. The appearance of the upper lip is short and thick, the upper front teeth protrude and the lower jaw retracts, and in severe cases, the upper front teeth cover the outer side of the lower lip, resulting in the upper and lower lips cannot be closed under normal conditions, and the upper front teeth are exposed outside the lip, forming the “open lip and exposed teeth” malocclusion. Without timely treatment, this condition will continue to worsen. Zhu Hong, Department of Stomatology, Beijing Children’s Hospital When a child is found to have the habit of biting the lower lip, parents should first not be impatient, because some children who bite the lower lip are timid, resentful and introverted, so they should first take psychological treatment methods, do not blame the child too much, take the child to participate in more group and outdoor activities, cultivate hobbies, and help the child gradually overcome the bad habit. If the child’s bad habits are stubborn and there are obvious dental and jaw developmental abnormalities, he or she needs to be seen in time for orthodontic treatment. This child was treated with muscle function braces for 6 months and obtained very good results. Before treatment: After treatment.